Self-Assessment Tax Organiser (UK)

Dreading your tax return? This spreadsheet turns a year of receipts into the exact figures you need for HMRC, and shows roughly what you'll owe before January arrives.

Built for UK sole traders, freelancers and landlords filing Self Assessment for 2025-26 (due 31 January 2027) or keeping records for 2026-27.

What it does

• Sorts your income and costs into HMRC's boxes for the self-employment (SA103S) and UK property (SA105) pages
• Tells you whether the £1,000 trading or property allowance beats claiming your expenses
• Estimates your Income Tax and Class 4 National Insurance, including the Personal Allowance taper
• Applies the 20% tax credit on mortgage interest for landlords
• Works out your payments on account and what to pay on 31 January and 31 July
• Calculates flat-rate mileage (45p for 2025-26, 55p from April 2026) and working-from-home allowances
• Handles joint ownership: log the full rent and it works out your share
• Shows income, costs and profit month by month, with a chart
• Flags mistakes: missing categories, dates outside the tax year, leftover example rows

What's inside (12 tabs)

Start Here · Setup · Return Figures · Tax Estimate · Monthly · Biz Income · Biz Expenses · Mileage · Home Office · Rental Income · Property Costs · Rates

Works with

Microsoft Excel, Google Sheets and Apple Numbers. No macros, no add-ons.

You'll receive

A .zip file with the spreadsheet (.xlsx) and a one-page quick-start guide, ready to download straight after purchase. Nothing is posted.

Good to know

• This is a record-keeping and planning tool, not tax advice. If your affairs are complicated, speak to an accountant.
• Rates and allowances were checked against GOV.UK in November 2026 and are listed in the file with sources.
• Income Tax estimates use England, Wales and Northern Ireland rates. Scottish taxpayers can use everything except the Income Tax lines of the estimate.
• Making Tax Digital: from 6 April 2026, sole traders and landlords with qualifying income over £50,000 must send quarterly updates using HMRC-recognised software. This spreadsheet can hold your records, but it isn't submission software.
• Doesn't cover savings, dividends, capital gains, student loans, pension contributions or capital allowances.